The invention deals with a camshaft for controlling valves in internal combustion engines. The cam shaft having at least one cam pushed upon the shaft and solidly connected thereto. The shaft having regions for the cams that have a larger diameter than the other regions of the shaft, and are provided with webs and beads formed by material displacement.
A camshaft of this type is described and shown in DE-OS 37 17 190, and a method for manufacturing such a camshaft is explained therein. The cams, which in this known design are pushed onto the shafts, are manufactured by sintering. The blank pressed from this sintered material is shaped so that the penetration into which the shaft must fit comprises radially projecting protrusions which extend across the entire axial length of the cam or the mentioned penetration. Herein several of such projections are provided so as to be uniformly distributed across the circumference of the penetration. As a consequence of the ledge or spring-like projections, the penetration is non-uniform across its circumference, meaning this penetration has several points at which an infinite quantity of tangents can be applied, at least theoretically.
The diameter of this penetration in the cam corresponds essentially to the diameter of the widened regions of the shaft, so that if the mentioned inner projections are non-existent, the cam could be slid upon the widened regions of the shaft without exerting any particular force. These ledge- or spring-like projections molded into the penetration, or their front end edge and end face viewed in sliding-on direction, have the task in this known design to act, as it were, as levers, and to serve to produce the groove when sliding the cam upon the shaft, which groove is required for the positive lock between the shaft and the cam. The slid-on cam is retained by pure positive lock upon the shaft in this previously known design. This known design can be remarkably rationally manufactured for camshafts with sintered cams.
Numerous motors exist, for which camshafts with forged steel cams are preferred and prescribed. Such steel cams are forged and subsequently tempered, in order to achieve a specific texture, the outer contour is hardened and the bore is drilled on a lathe. It is impossible with such forged steel cams to provide ledge- or spring-like projections as can be achieved with sintered cams, without significant effort. In a steel cam, the bore must be remachined with a cutting tool bit in order to create such projections, for instance it would have to be broached. Such a manufacturing step is impractical because of costs. For such a machining process the costs would be considerably increased compared to those which would have to be necessarily expended for a forged cam.
On the other hand, applicant is aware that a camshaft with sintered cams and the previously described construction can be manufactured economically, so that the aim exists to strive for a comparable manufacturing method also for camshafts with forged steel cams. However, cost considerations, as stated above, stand counter to this desire.